Pigment and method of producing same



' PETER FIREMAN, OF TRENTON, NEW JERSEY, ASSIGNOR TO MAGNETIC PIGMENT COMPANY, A CORPORATION OF NEW Y0 PIGMENT AND METHOD OF PBODIICIN G SAME.

Lea aces.

No Drawing.

To all whom it may concern:

Be it known that I, Dr. PETER F IREMAN, a citizen of the United States, residing at Trenton, in the county of Mercer, State of New Jersey, have invented certain new and useful Improvements in Pigments and Methods of Producing Same; and I do hereby declare the followin to be a full, clear, and exact'description of the invention, such as will enable othersskilled in the art to WlllCh it appertains to make and use the same.

his invention relates to colored pigments produced by oxidation of ferrous hydroxide under suitable conditions and has for ts particular object the production of relatively inexpensive yellow and brown p gments of fine texture and color and appllcable to a wide variety of purposes.

The numerous advantages of the invention will be apparent upon examination of the specificatlon, in which I have defollowing f d o proce scribed several preferred modes ure. It is to be understood that the description of my invention is illustrative merely, and that various modifications'may be introduced through variation of the specified materials, their relative proportions and the temperatures employed, within the scope of the accompanying claims, it being my intention to claim as my invention the procedure whereby the advantageous results hereinafter described are accomplished.

When freshly precipitated ferrous hydroxide is oxidized a variety of products result dependinguponvarious factors. Normally when the reaction occurs uncontrolled, ina solution from which the hydroxide is precipitated, a black precipitate of ferroferric oxide is produced which is undesirable for the purposes of my present invention. I have discovered that by variations of the completeness ofprecipitation of the iron and of the temperature, under which oxidation of ferrous hydroxide is carried out, the reactions may be directed-to produce a number of valuable pigments. By the utilization therefore, of suitable precipitating reagents in predetermined proportions and the employment of air or other containing oxygen as an oxidizing agent,

.under controlled temperature conditions, I

am able to produce the desired pigments in an effective, inexpensive and expeditious manner.

The character as well as the relative proportion-of the precipitating reagent has a Specification of Letters Patent. Application filed-May 31,

Patented Aug. 1, 1922. 1919. Serial no. 301,028.

marked effect upon the resulting product and the temperature of the reaction must be carefully controlled to produce the desired recalcium hydroxcontaining oxygen are also available for the purpose,'air being preferred'because it is effective and freely available. Suflicient steam is preferably introduced with the air to produce the desired temperature, the amount steam being carefully regulated, so that the temperatures do not'rise above a predetermined maximum and the increase in temperature occurs gradually and over a considerable period of time. out in any suitable container or tank, preferably constructed to permit the distribution of air and steam through the solution. As specific examples of the application of my invention, I shall describe the tion of both yellow and brown pigments from solutions of ferrous chloride, To produce a yellow pigment, an aqueous solution of ferrous chloride of prefcra y about 1.060. specific gravity, is treated'wi bonate. The sodium carbonate is preferably added in a solid state, but may be previously dissolved. Preferably before the addition of the sodium carbonate, a lively current of air is blown through lution, with little steam only. The sodium carbonate is added in considerable excess while the current of air and steam continues. The heating of the solution by the steam is carried out at a rate which permits the tem- 100 rous iron is converted into ferric iron. Suflino clent steam is then admitted to raise the temperature of the solution to the boiling I prefer'to employ a mother liquor of a precipitating reut it is to be un- 66 s employed as the oxidizing material although oxygen or mixtures 70 The reaction is carried 80 produc- 86 h sodium car 90 the ferrous chloride soat is regulated 'so that the point which is maintained for substantially into a dilute solution of ferrous chloride to one half hour. The latter step, while not eswhich calcuim hydroxide has been added in sential, facilitates the filtration of the prodquantity sufficient only to partially precipiuct. tate the iron. Steam is supplied with the air 5 In the course of the reaction, the fresh preto raise the temperature to substantially 7o cipitate of ferrous hydroxide is first light 105 F. and oxidation is completed between blue in color, then greenish blue, andfinally this temperature and substantially 130 F. acquires a yellowish tinge. Upon the con- The oxidation will be complete in the course tinuation of the reaction, the precipitate of a few hours and by'varying the degree of yellow which is characteristic of the final tained covering a range of tan shades, the product. The precipitate is filtered, washed pigment being voluminous and lustrous in and dried in any suitable manner, the drycolor. The conditions surrounding the reing being preferably accomplished by means action must be carefully guarded, inasmuch of steam coils and a product is obtained as, if heated too energetically, black ferro which is of low specific gravity and provides ferric oxide is produced, which on continued a clear yellow pigment of great color oxidation yields a brown product, harsh in strength. texture and devoid of lustre.

v In an alternative form of my invention As above pointed out, sodium carbonate 20 adapted to produce a yellow pigment, caland calcium hydroxide are mentioned merecium hydroxide is employed in place of the ly as indicative of the materials readily sodium carbonate. The ferrous chloride soavailable and best adapted to the accomlution having a specific ravity of 1.060 to plishment of the desired result. Other solu- 1.090 is treated with suicient calcium hyble hydroxides or carbonates may be substi- 25 droxide to precipitate from 7 5 to of the tuted and the proportions and temperatures iron. Air and steam are introduced during mentioned may be vari ddependentupon the the precipitation of the iron, the steam being strength and character of the reagents emregulated so that the temperature is not per ployed to produce a variety of well defined mitted to rise above substantially F. pigments.

30 until oxidation is sufficiently complete The foregoing examples will be sufficient 5 to bring the ratio of ferrous to ferric iron to enable anyone skilled in the art to pracin the precipitate to substantially 120.5. tice the invention and produce pigments of The amount of steam is then gradually inthe color and character described herein, but

creased until the boiling temperature is it is to be understood that various other pigsubstantially complete. through variation of the factors enumerated. The precipitate, at first light blue, be: Such variations are within the scope of my comes darker in shade. Then as the reaction invention, which depends upon the discovcontinues, the color lightens, becomes greenery that the products resulting from the ox- .40 ish, then yellow in tinge and finally the preidation of freshly precipitated ferrous. hycipitate assumes a clear yellow color. After droxide may be varied in color and texture filtering, washing and drying, the latter opby suitable regulation of the temperature at eration being conducted at substantially which the oxidation is'carried out. 100 F., a voluminous yellow pigment of From the foregoing it will be readily ap- 1 45 fine texture is obtained. preciated that I am able, through the oper- In the production of brown pigments, I ation of my invention to produce desirable preferably employ a solution of ferrous chloigments at a relatively slight expense and ride of a specific gravity of substantially 1.070 in quantity sufficient to meet increasing deand add thereto sodium carbonate in quanmands for material of this character. The 50 tity sufficient to produce an alkaline reaction, raw materials for the production of pigduring the introduction or air, and steam. ments in accordance with my invention are The temperature is controlled so that it does readily available in the market and may be not rise above 110 F. during the first hour of obtained in any quantity desired and at operation, where the volume of solution is relatively low cost. No peculiar apparatus lit-sufficient to produce one ton of the product. is essential to the operation of the vinv'en- The supply of steam is carefully regulated so tion and it is deemed unnecessary to illusthat the solution gradually approaches the tr'ate or describe an apparatus for use in boiling temperature, which is reached after connection therewit inasmuch as any 3 or more hours and oxidation is continued chemist will readily devise from materials 60 at this temperature until substantially comat hand, suitable apparatus for carrying out 1211 plete. The product. after filtering, washing the invention on any desirable scale? and drying is a brown pigment of velvety I claim:

texture and brilliant color. a 1. A method of preparing colored pig- The procedure may be varied to produce ments, which comprises precipitating for- 65 a brown pigment by passing a current of air rous hydroxide from an iron-containing 13 10 becomes brownish yellow and finally a clear temperature, a series of pigments are ob- 5 i 35 reached and is continued until oxidation is -ments of a similar character may be produced 0 solution, oxidizing the precipitated ferrous solution, oxidizin the precipitated ferrous hydroxide inthe mother liquor and 'conhydroxide in the eated mother liquor and trolling the oxidation by limiting the temcontrolling the temperature of the mother perature of the mother liquor during the liquor so that it does not materially exceed 85 '5 early stages of oxidation to a point below 110 F. during the early stages of oxidathat at whiehbla'ck oxides form. v ,tion to avoid the formation of'black oxides. 2. A method of preparing colored pig- 5. As new articles of manufacture, the ments, which comprises adding toan ironherein described colored pigments of volcontaining solution a reagent capable of -uminous body and brilliant color, consist- 40 1o precipitating iron as. ferrous hydrox1de,1ning of the products of oxidation in the jecting a gaseous. oxidizing and heating mother liquor of precipitated ferrous hy-- medium into the mother liquor containing droxide at a temperature which does not the ferrous hydroxide and controlling the exceed 110. F. during the early stages of i oxidation b limiting the quantity of the oxidation. 15 gaseous me ium injected durin the early 6. A method of preparing brown pigment stages ofo'xidation to maintain t e temperawhich comprises adding to a solution of fer- ;ture of the mother liquor at a point below rous chloride sufficient sodium carbonate to that at which black oxides form? produce an alkaline reaction, partially oxi- 3. A method of preparing colored pigdizing the-precipitated-ferrous hydroxide at 2o ments, which comprises precipitating fer-, a temperature of substantially 110 F. and ions hydroxide from an iron-containing completing oxidation at adually increas-. solution by adding sodium carbonate therein temperatures approac 'ng 212 F. to, oxidizing the precipitated ferrous hyg s an article of manufacture, a brown dioxide in the mother liquor and controlling pigment of brilliant color consisting of oxi- 25 the oxidation by limiting the temperature dized precipitated-ferrous hydroxide.

of the mother liquor during the early stages 8. As an article of manufacture, a volumi of oxidation to a point below that at which nous pigment of brilliant color consisting black oxides form. of oxidized precipitated-ferrous hydroxide.

4. A method of preparing colored pig In testimony whereof'I aflix iny signature. 3o ments, which comprises precipitating ferrous hydroxide from an iron-containing PETER FIREMAN. 

